In cat D airspace do pilots find it useful or a pain to be advised of non mode c equipped but transponding aircraft (generally vfr and usually known and NON conflicting).I ask because a lot of traffic in and around the TMA I work in does not have an altitude reporting facility and I always personally took the view that if I knew about it I would (time and other tasks permitting) rather advise the aircrew rather than they ask.Regards